Use and Importance of Piping and Instrumentation

Diagrams (P&IDs)

Steven T. Maher, PE CSP

Risk Management ProfessionalsU.S. 877/532-0806 ♦ www.RMPCorp.com

Download Presentation & Handout – www.SEMS1.com/BSEE.Mar15.htm

TOPICS

• Use of P&IDs• Key Elements• Importance of Quality P&ID’s During a HAZOP

Study• Signs that a P&ID has not been Field-Verified

Use of P&IDs

Purpose of a P&ID

• It is a representation of a process or system and how it functions.– Depicts the sequence between components within the

process.– Provides information on instrumentation and equipment

interface– P&IDs are not a physical or mapping representation of the

system (Two items side by side on a P&ID can actually be in different buildings or on opposing sides of the process plant.)

• A picture paints a thousand words

Utilizing P&ID’s

• P&IDs are a useful tool during a HAZOP – Enable the Team to understand the process – Allow for systematic evaluation based on

representative P&ID flows (Node development)• Enables to keep the Team focused and aligned

– Valve/equipment identification (tag) numbers in P&ID synched with HAZOP report documentation

• Facilitates identification of safeguards– Process design and conditions defined in P&IDs

used to evaluate the process during the HAZOP

– Can be used alongside other useful maps and diagrams for a comprehensive HAZOP

• Process Flow Diagrams• Cause and Effect

Diagrams• Electrical Diagrams• Site Maps• Chemical Detection/

Monitoring Maps

Utilizing P&ID’s (cont)

Key Elements

Summary of Key Elements

• General P&ID layout• Legend• Piping• Valves• Instrumentation• Equipment

P&ID Layout

Grid

• Grid enables reader to easily locate equipment, valving, etc, for complex P&IDs.

Information Blocks

REVISION BLOCK

TITLE BLOCK

• Title block enables identification of system and drawing numbers

• Revision block provides information on history of changes to process.

P&ID Legend

Legends•A legend is useful to understand the P&ID

–Defines symbols with corresponding piping type, equipment type, valve type, etc.–Provides alignment of individuals participating in the HAZOP

Piping

Piping - Common Line Symbols

Line Identification

Pipe Line Size

Service Designation

Line Identifier

Pipe Spec.

Insulation

Not Insulated

Heat Tracing

Line Identification-C1 -I -X -HT6" -CWS -301

Provides detailed information of the process flow piping design and specifications.

Valves

Valve Symbology

Type:– Gate Valve

– Globe Valve

– Ball Valve

– Butterfly

– Needle

Different types of internal mechanical configurations include:

Sample Symbol:

Type:

– Multiport Valve

– Angle Valve

– Check Valve

– Pressure Relief Valve

Other common valves

Sample Symbol:

Valve Conditions

Positions:

Normally Closed Valve NC

Normally Open Valve NO

Locked Open Valve LO

Locked Closed Valve LC

NC

Variance In Valve Designations

NC

Closed ValveNormally 

Closed Valve Globe Valve Globe Valve

Valve Failure Modes

Fail Position:

Fail Closed FC

Fail Open FO

Fail Last FL

Fail In Place FI

FC

Instrumentation

• Process plants consist of instrument loops (control valve assemblies) which are designed to maintain a process variable (pressure, flow, level, temperature) within an defined operating range.

• Instrument Loop Components– Sensor– Transmitter– Controller– Actuator

• Additional Instrumentation– Gauges– Indicators and Recorders

Instrument Loops

Valve Actuator Types

• Solenoid

• Diaphragm

• Motor

• Piston

Type: Sample Symbol:

Instrument, Logic & Computer Symbols

Discrete Instrument

DCS: Distributed Control System

PLC: Programmable Logic Control

Instrument Identification and Tag Numbers

TT101

Function Identification(Instrument Type)

Sequence (Tag) Number

• Each instrument type should have a unique sequence number.

• Similar convention applies to valving and equipment, all must have unique identification.

Instrument Nomenclature

Process Measurement

Element Type Element

Transmitter Indicator

Indicator controller Controller

Control Valve Recorder

Code E T I IC C V R

Analysis A AE AT AI AIC AC ACV AR

Flow F FE FT FI FIC FC FCV FR

Level L LE LT LI LIC LC LCV LR

Pressure P PE PT PI PIC PC PCV PR

Delta Pressure dP dPE dPT dPI dPIC dPC dPCV dPR

Quantity Q QE QT OI OIC QC QCV QR

Temperature T TE TT TI TIC TC TCV TR

Delta Temperature dT dTE dTT dTI dTIC dTC dTCV dTR

Vibration Y YE YT YI YIC YC YCV YR

Position Z ZE ZT ZI ZIC ZC ZCV ZR

Instrument Nomenclature

Process Measurement

Element Type

Ratio Calculation

Switch Low

Switch High

Alarm Low

Alarm Low Low

Alarm High

Alarm High High

Code FY SL SH AL ALL AH AHH

Analysis A AFY ASL ASH AAL AALL AAH AAHH

Flow F FFY FSL FSH FAL FALL FAH FAHH

Level L LFY LSL LSH LAL LALL LAH LAHH

Humidity M MFY MSL MSH MAL MALL MAH MAHH

Power N NFY NSL NSH NAL NALL NAH NAHH

Pressure P PFY PSL PSH PAL PALL PAH PAHH

Delta Pressure dP dPFY dPSL dPSH dPAL dPALL dPAH dPAHH

Quantity Q QFY QSL QSH QAL QALL QAH QAHH

Temperature T TFY TSL TSH TAL TALL TAH TAHH

Delta Temperature dT dTFY dTSL dTSH dTAL dTALL dTAH dTAHH

Vibration Y YFY YSL YSH YAL YALL YAH YAHH

Position Z ZFY ZSL ZSH ZAL ZALL ZAH ZAHH

Instrument Loop Example

Flow Element

Flow Transmitter

Flow Controller

Flow Control Valve

Equipment

• Key process equipment:– Accumulator – Separator– Reactor– Fractionating Columns– Heat Exchanger – Air-Fin Coolers– Heater– Compressor– Pump

• Names and types vary based on the industry they’re used.

Equipment

Importance of Quality P&ID’s During a HAZOP Study

High Quality P&ID’s

• Accurate and Detailed P&IDs allow for high quality and efficient HAZOP sessions – Enables the Team to better define and evaluate scenarios– Results in valuable Recommendations vs “verify”

Recommendations• Key Information on P&IDs enable the Team to identify

areas of concern that may otherwise be overlooked during the HAZOP

• Common link between the HAZOP and process documentation/procedures (e.g. PSI, SOP, MI)

• Prevent LARGE headaches during 5yr revalidations or MOC HAZOP Studies.

Key P&ID Information

• Piping information:– pipe size– materials of construction, design conditions– spec breaks– heat tracing– insulation

• Enables the Team to determine the adequacy of pipe for service and special considerations– Corrosion– Runaway Reactions– Changing process flow

Key P&ID Information

• Equipment information:– type – size – material of construction– Pipe and equipment design conditions

(temperature and pressure)

Key P&ID Information

• Instrumentation and Controls information:– Instruments

• Monitoring (local or control room)• Controlling (valve local, instrument in control room)• Emergency( Local or Control Room)

– Alerting– Automatic Action

Key P&ID Information

• Complete Instrumentation and Controls information:– Helps define

the process– Enables the

Team to verify the failure modes

– Enables the Team to understand controls/interlocks

PIC-1

FC FO

PSV-1

PCV-1A PCV-1B

Key P&ID Information

• Safety Systems information:– Safety Systems

• Relief Valves• Flare Systems• Emergency Trips and Actions

– Information on the settings and actions of safety systems should be identified

Signs that a P&ID has not been Field-Verified

Inaccurate P&IDs = Invalid HAZOP Study

• Indications that a Field Verification is necessary– Revision block and dates on P&ID not current

(although changes have been made)– Outdated equipment information– Flow streams do not make sense

Prior to HAZOP

• Investigative work prior to scheduling the HAZOP– Review MOC’s– Interview Operations and Maintenance

personnel to identify process changes– Update controls summary and C&E’s as

necessary– Field verify any changes and “spot-check” a

section that has not been changed for accuracy

Questions?

Steven T. Maher, PE CSPSteve.Maher@RMPCorp.com

877/532-0806www.RMPCorp.com

Risk Management Professionals